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Heated Bed for M3D 3d Printer

Usb phyton controlled heated bed for M3D 3d printer, making abs printing possible

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Since the first day I got my hands on an m3d 3d printer all I wanted to do was to print with abs. Why? Because you can't. So I decided to make a heated bed and a few tweaks to the printer making abs printing possible. While doing that tried to make sure that the printer keeps running and project's cost aligns with m3d's cost of 350$.

Short story screwed a few resistors and taped a thermistor (with kapton) under an aluminum sheet cut as similar as possible to m3d's original bed. Drilled a few holes on m3d to get the wires out and connected them to another project of mine RestIO along with an old laptop power suppy and a mosfet. Typed a few lines of phyton calling rest api of Rest IO reading the temperature and driving the fet.

Heated Bed for M3D

I made this project as a heated bed is the most reliable way of printing ABS models with extruding 3d printers. ABS is less brittle than PLA and a bit more heat resistant. M3D printer comes with a very impressive price of 350$ but also with a bunch of missing features such as an heated bed which is almost a must for ABS printing. I wanted to build a heated bed that aligns with printers price tag. I have seen other projects and campaigns but I don't see the logic behind spending 100$ on a heated bed for a 350$ printer. Ended up with a working heated bed and successful ABS prints and learned a lot about 3d printing through the journey. The cost of the project is around 25$ at most.

WARNING & DISCLAIMER

This project adds a very hot feature to a very cheap product which is originally not engineered for delivering this hot feature. There are many things that can go wrong and catch fire so please don't attempt unless you fully understand what you are doing. Never leave it unattended and keep your nostrils open for interesting smells. Even of you do everything right and safe still I don't think I can explain what I did to my printer to m3d's customer support in case I need them. Having said that I have printed more than 100 hours with this heated bed on around 90C and nothing went wrong so far. Well nothing that can't be fixed with superglue : )

M3D Printer

Don't want to get too much into what this printer is and can do but thanks to a friend who grabbed one for me from their kicktarter campaign. It's mostly advertised as beginner friendly equipment. In some ways it is but guess the overall technology is still quite far from that statement. Having said that even I have spent ridiculous amount of time without any print that looks like anything it has been quite a nice adventure. Learnt a lot about the challanges of 3d printing and this particular device.

ABS Printing

I actually had dozens of decent results with PLA with M3D. Not everything works as you would like to but it's fair to say out of the box, m3d can print rather simple PLA models without a lot of knowledge on 3d printing. Didn't took me long to try ABS and miserably fail. Tried a lot of ways to print ABS before starting on this project but after first tests I was really impressed as actually I wasn't expecting the heated bed to make such a vast difference in overall quality and ease.

Tips & Tapes

I wrote about these in the instructions as well but for the lazy reader a few tips I need to underline.

  1. I prefered blue painters tape over kapton as it was hard to apply kapton properly, hard to calibrate the printer achieve the necessary precision, and requires higher temperatures, mixed results with PLA. This bed heater heats the bed but also heat abs parts and electronics of the printer. I wanted to keep the thermal stress on printer minimal. Blue tape was more forgiving even at 85 C I had good results with ABS plus I had great results with PLA as well without even heating.
  2. A fan over the feeder is compulsory. Without it the feeder gets too hot eats into the filament too much and stops feeding the filament to the extruder. Check the pictures and instructions. And please turn the default fan of the M3D off before ABS prints as it will sabotage your print cooling layers too fast. Some small prints may require cooling but mostly not. You will have other problems anyways printing small parts with ABS regarding precision.
  3. Before printing ensure printer can extrude. Just from advanced mode section of M3D software heat it to ABS temperature and extrude until some filament comes out. Do this everytime before print. For some reason after print M3D retracts the filament and ABS also shrinks as well usually resulting no first layers for your next print.
  4. Couple of things I did are optional or rather experimental. Like you probably don't need three resistors. Or you may come up more for better thermal distrubution. You don't need the control the extra fan but it's nice to control it....
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  • 1 × 18 gauge Aliminum sheet
  • 3 × 5.6R 25W Power Resistor
  • 3 × 10K Resistor
  • 2 × 220R Resistor Electronic Components / Misc. Electronic Components
  • 2 × 47 uf Capacitor

View all 9 components

  • 1
    Step 1

    Prepare the bed

    • Cut a 132x130 mm rectangle from aluminum sheet using your favorite cutting tool.
    • Sand one edge (130 mm in length) patient enough to get the outline resemble m3d original bed forming ears that will slide into place just like the original bed. This requires some patience based on your tools and skills but quite easy. Just sand until you have a rectangle as close as possible to original bed in shape and fits tightly into m3d.
    • Optional step. Cut another piece 85x85 mm. This piece will be under the big piece mounted as in the image. It provides easier mounting for resistors with screws as it provided more thickness I needed and some heat capacity which may or may not be a good thing. Also sand it a bit so no rough edges.
  • 2
    Step 2

    Power Resistors

    This pretty much relies on the power supply you choose. I used three 5.6 ohm resistors 2 in parallel and one in series totaling to 8.4 ohm resistance overall on paper. When I divide my supplies voltage 19.5V to 8.4 ohms I get aprox. 2.3A as current which is within limits of the supply and looks like adequate amount of heating power. Also keep an eye on your resistors power rating and try to stay below them. Resistors I used were rated at 25 watts which is more than enough based on this calculation.

  • 3
    Step 3

    Mounting resistors and panel

    If you have the second 85 mm square sheet cut as well place it in the middle of the bigger cut sheet. You can temporarily use tape to stick them together and make sure they fit into the printer together. If they don't check what prevents a nice fit and adjust smaller sheet position and try until you hit the sweet spot. Don't assemble anything or drill any holes before ensuring the bed will nicely fit into the printer. Once you are happy with the fit and position of the smaller piece draw a border around it and start drilling holes for your resistors. 2 mm deep if you have used 18 gauge sheet. So the idea here is not to drill through both sheets. Use a hobby drill or similar easy to control tool. Also ensure the holes are tight so the screws will hold strong. And be patient. Length of your screws depends on your resistors thickness around mounting holes and plus 2 mm depth of the bed or whatever it is. Not as tricky as it sounds but certainly requires some patience plus trial and error.

    Before screwing everything apply a thin layer of heat transfer paste in between everything. Between big and small plate as well as between small plate and resistors.

    And at last stick a 10k thermistor with kapton tape keeping a fair distance to resistors. Make sure it's legs are not shorted by aluminum sheet. So use heat shrink or heat resistant insulation to prevent that. I used heat shrink. Highly recommended no issues.

    If what you did looks like below, your resistors are tight in place and this whole panel can fit tightly into the printer then hardest part is over.

View all 6 instructions

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omkarkarve wrote 08/04/2017 at 20:34 point

I dont have much experience in reading electrical circuits. Can you show a connection diagram? I cant see where the thermistors are wired?

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